CVE-2017-7902 in MicroLogix 1100
Summary
by MITRE
A "Reusing a Nonce, Key Pair in Encryption" issue was discovered in Rockwell Automation Allen-Bradley MicroLogix 1100 programmable-logic controllers 1763-L16AWA, Series A and B, Version 16.00 and prior versions; 1763-L16BBB, Series A and B, Version 16.00 and prior versions; 1763-L16BWA, Series A and B, Version 16.00 and prior versions; and 1763-L16DWD, Series A and B, Version 16.00 and prior versions and Allen-Bradley MicroLogix 1400 programmable logic controllers 1766-L32AWA, Series A and B, Version 16.00 and prior versions; 1766-L32BWA, Series A and B, Version 16.00 and prior versions; 1766-L32BWAA, Series A and B, Version 16.00 and prior versions; 1766-L32BXB, Series A and B, Version 16.00 and prior versions; 1766-L32BXBA, Series A and B, Version 16.00 and prior versions; and 1766-L32AWAA, Series A and B, Version 16.00 and prior versions. The affected product reuses nonces, which may allow an attacker to capture and replay a valid request until the nonce is changed.
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Analysis
by VulDB Data Team • 12/25/2020
The vulnerability described in CVE-2017-7902 represents a critical cryptographic weakness in Rockwell Automation's MicroLogix series programmable logic controllers that directly impacts the security of industrial control systems. This issue falls under the category of cryptographic implementation flaws, specifically addressing the improper handling of nonces in encryption operations. The affected devices include various models from both the MicroLogix 1100 and 1400 series, all running firmware versions 16.00 or earlier, which suggests a widespread exposure across multiple product lines. The fundamental problem lies in the reuse of nonce-key pairs during encryption processes, creating a predictable pattern that adversaries can exploit to compromise system integrity.
The technical flaw manifests when the same nonce is used with the same encryption key across multiple operations within the controller's communication protocols. This cryptographic weakness enables attackers to perform replay attacks by capturing valid encrypted communications and reusing them at a later time. The reuse of nonces violates fundamental cryptographic principles where nonces must be unique for each encryption operation to maintain security properties. According to the CWE database, this vulnerability maps to CWE-330, which specifically addresses the use of weak or predictable random numbers in cryptographic operations. The implications extend beyond simple data interception, as these controllers operate in critical infrastructure environments where unauthorized access could lead to operational disruption or safety hazards.
The operational impact of this vulnerability is significant within industrial environments where these controllers manage critical processes. Attackers who successfully exploit this weakness can potentially gain unauthorized access to control systems, manipulate process variables, or execute malicious commands without detection. The ability to replay valid requests until the nonce changes creates a window of opportunity for attackers to maintain persistent access, particularly in environments where controllers may not be frequently rebooted or where nonce rotation occurs infrequently. This vulnerability directly relates to ATT&CK technique T1071.004, which covers application layer protocol communication, and T1566, which addresses credential access through network sniffing and replay attacks. The affected systems represent critical infrastructure components in manufacturing, process control, and automation environments where the consequences of unauthorized access can be severe.
Mitigation strategies for this vulnerability require immediate firmware updates from Rockwell Automation to address the nonce reuse issue in affected controller models. Organizations should implement network segmentation and monitoring to detect unusual communication patterns that might indicate replay attacks. The implementation of additional authentication mechanisms beyond the existing cryptographic framework can provide defense-in-depth. Security teams should conduct comprehensive inventory assessments to identify all affected devices across their industrial control networks and prioritize remediation efforts based on risk exposure. Regular security assessments and vulnerability scanning should be implemented to identify similar cryptographic weaknesses in other industrial control systems. The vulnerability highlights the importance of proper cryptographic implementation in embedded systems and underscores the need for robust security practices in industrial environments where the stakes of security failures extend beyond traditional information technology concerns.